Dead Salmon 'Responds' to Pictures of People

A dead salmon has become a scientific celebrity after its brain
supposedly lit up when shown pictures of humans during a brain scan.

Some bloggers last week reported that the fish was still thinking or that the research is evidence of an ethereal soul. However, the study was done to show that data from an fMRI brain scan can lead to false positives — misleading results — if not carefully analyzed.

Yes, the salmon was dead — bought in a lifeless state at a fish
market and scanned an hour later. No, the results are not shocking or
miraculous. Like many scientific studies, the study and its results,
presented earlier this year in a poster at a conference, are technical
and rather bland:

"The goal of the salmon poster was to encourage the minority of
researchers who report uncorrected statistics to move forward and begin
using basic multiple comparisons correction in their research," says
study leader Craig Bennett, a postdoctoral researcher in the Department
of Psychology at the University of California, Santa Barbara.

In a nutshell, the data reported by Bennett and colleagues in no way
suggests the salmon's brain was functioning, but rather reveal
anomalies that can be misleading if you're not careful. [In a separate
study recently, researchers concluded that human brain scans are often done unnecessarily.]

Scientific saga

The scientific saga of the salmon is as long and complex as a salmon's journey from the ocean to a mountain stream to spawn.

It began in 2005 when Bennett picked up a salmon at a local market.
An hour later he and colleagues stuck the fish in an fMRI scanner and
did a bunch of different scans as part of a project at Dartmouth
College to develop MRI protocols. They had previously scanned a pumpkin
and a dead bird.

"The salmon was approximately 18 inches long, weighed 3.8 lbs, and
was not alive at the time of scanning," the poster presentation states.
"The salmon was shown a series of photographs depicting human
individuals in social situations with a specified emotional valence.
The salmon was asked to determine what emotion the individual in the
photo must have been experiencing."

"By far it was our crowning achievement in terms of ridiculous
objects to scan," Bennett recently wrote, on his blog, of the fish.

Another look at the data

Then in 2008, Bennett was working with one of his advisers on a
presentation about false positives in MRI data, specifically about
misleading results that can come from what's called a "multiple
comparisons problem." Bennett ran his 2005 fish data through some
statistical programs and, sure enough, three false positives showed up
in the salmon's brain.

The results were presented at the Human Brain Mapping conference
last June in San Francisco. They almost never saw the light of day,
however. In the review process, "Just about everyone thought it was a
joke — some rogue student who was playing a prank," Bennett says.

The findings have been submitted to a journal — as a cautionary tale
about data interpretation — but not yet accepted for publication (it is
normal for scientific papers to go through a months-long process of
review, rewrite and resubmission).

With all of last week's hoopla, Bennett blogged about some of the
best comments he ran across regarding the dead salmon study. Here is
one he considers spot on: "The recorded signal is changing due to
noise. The point of the experiment is that if you look at enough
signals, the noise in one will match the timing of your experimental
stimulus, purely out of chance."

In The Water Cooler, Imaginova's Editorial Director Robert Roy Britt looks at what people are talking about in the world of science and beyond.Find more in the archives and on Twitter.

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Author Bio

Robert Roy Britt

Rob was a writer and editor at Space.com starting in 1999. He served as managing editor of Live Science at its launch in 2004. He is now Chief Content Officer overseeing media properties for the sites’ parent company, Purch. Prior to joining the company, Rob was an editor at The Star-Ledger in New Jersey, and in 1998 he was founder and editor of the science news website ExploreZone. He has a journalism degree from Humboldt State University in California.